[PATCH 1/3] mm: check negative error of folio_isolate_lru() when failed to isolate a folio

[Baolin Wang]

The folio_isolate_lru() will return a negative error if failed to isolate
a folio from its LRU list, thus better to check the negative error to
make the code more clear per Linus's suggestion[1].

No functional changes.

[1] https://lore.kernel.org/all/CAHk-=wiBrY+O-4=2mrbVyxR+hOqfdJ=Do6xoucfJ9_5az01L4Q@xxxxxxxxxxxxxx/

Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
---
 mm/damon/paddr.c | 2 +-
 mm/gup.c         | 2 +-
 mm/khugepaged.c  | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index b4df9b9bcc0a..ebf3dd084af2 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -246,7 +246,7 @@ static unsigned long damon_pa_pageout(struct damon_region *r, struct damos *s)
 
 		folio_clear_referenced(folio);
 		folio_test_clear_young(folio);
-		if (folio_isolate_lru(folio)) {
+		if (folio_isolate_lru(folio) < 0) {
 			folio_put(folio);
 			continue;
 		}
diff --git a/mm/gup.c b/mm/gup.c
index b0885f70579c..7fdddd43663c 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1939,7 +1939,7 @@ static unsigned long collect_longterm_unpinnable_pages(
 			drain_allow = false;
 		}
 
-		if (folio_isolate_lru(folio))
+		if (folio_isolate_lru(folio) < 0)
 			continue;
 
 		list_add_tail(&folio->lru, movable_page_list);
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index a5d32231bfad..463dfca4b841 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2047,7 +2047,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
 			goto out_unlock;
 		}
 
-		if (folio_isolate_lru(folio)) {
+		if (folio_isolate_lru(folio) < 0) {
 			result = SCAN_DEL_PAGE_LRU;
 			goto out_unlock;
 		}
-- 
2.27.0